Untangle confusion regarding POP source tagging.

[johanix]

in the pop-sources.yaml file an MQTT source has a bunch of metadata that describes format and where it is coming from. In particular the fields (and their current values):

source: mqtt
format: tapir-msg-v1

are what we have right now. We don't really use the "format" tag anywhere (but I think we should, to make it possible to in the future if needed change the JSON that is sent from Core). And the "source" tag is used initially (to detect this as an MQTT source and send it into the right source parsing code. But then we lose the source (and the format) in the resulting structs.

This is a problem, because in the debugging end there is a command ("tapir-cli debug colourlists") that shows the contents of the various "WBGlists" that POP uses internally. That command produces mostly unreadable output. To be able to present the contents of each list in an understandable manner we must know the format, i.e. we need the "source" and "format" data which was lost somewhere.

It would be great if that could be fixed asap, as that is rather important in preparation for the next demo.

[zluudg]

Attempted to address this in dnstapir/cli#18. Let me know what you think. Is it enough?